1. Field of the Invention
The present invention relates to an apparatus for securing magnetic poles of magnet-type rotating machines in which permanent magnets are used as field magnetic poles.
2. Description of the Prior Art
FIGS. 2 and 3 show in combination a conventional apparatus for securing magnetic poles of magnet-type rotating machines which is disclosed, for example, in Japanese Utility Model Public Disclosure No. 60-79231 (1985). In the Figures, the reference numeral 1 denotes a yoke which defines a cylindrical fixed frame. A plurality of permanent magnets 2 which serve as main poles are attached to the inner surface of the yoke 1 by means of positioning members 4 (described later). Auxiliary poles 3 which are formed of sort iron strip are firmly connected to the inner surface of the yoke 1 by electric resistance welding method or the like. Each of the auxiliary poles 3 is firmly attached to each of the magnets 2 at the side of increasing magnetic flux (magnetic flux for armature reaction) which is generated by a rotor (not shown). The numeral 4 denotes positioning members each defined by an elastic member formed into a substantial U-shape in cross section with its side walls 4a extending toward the open end. Each positioning member 4 is press-fitted into the space defined between one magnet 2 and the auxiliary pole 3 facing thereto, whereby the side walls 4a push the magnets 2 to bring them into close contact with the inner circumferential surface of the yoke 1. The pair of side walls 4a of each positioning member 4 are respectively provided with first and second pairs of notches, the distance between the first pair of notches corresponding to the axial length of the magnet 2, and the distance between the second pair of notches corresponding to the axial length of the auxiliary pole 3. Thus, when the positioning member 4 is press-fitted into the space between the magnet 2 and the auxiliary pole 3, the axially projecting portions 4b of the positioning member 4 project from the axial end faces of the magnet 2 and the auxiliary pole 3 and, at this time, the projecting portions 4b have a width larger than a clearance between the magnet 1 and the auxiliary pole 3, thus axially supporting the magnets 2.
The conventional magnetic pole securing apparatus arranged as described above suffers, however, from the following problems. Namely, before the positioning member 4 is press-fitted into the space between the magnet 2 and the auxiliary pole 3, it has a tub-like shape, i.e., a slightly outwardly opened U-shape in cross section, as shown in FIGS. 4 and 5. For this reason, before the positioning members 4 are assembled to the yoke 1, for example, during transportation, individuals in a stack of a plurality of positioning members 4 undesirably come into fitting engagement with each other as shown in FIG. 5, and therefore it is necessary to disengage them from each other at the time of assembling. Such fitting engagement between stacked positioning members 4 causes a particularly critical problem in the case of an automatic feed system employing a parts feeder or the like.